All of them have opened fitness centers, part of a growing trend around the country. Gyms fill space, generate revenue for struggling centers and bring in people – although it appears many folks don't spend much extra money after they finish working out.

When Planet Fitness opened at Orlando Fashion Square late last year, it filled a gaping hole in the mall. It went into a wing where several stores had departed over the past couple of years, filling 18,500 square feet.

But "they don't really come in and buy coffee," said Bibi Alli, an assistant manager at the mall's Barnie's. "If they come in, they get little samples."

She said she gets more business from a worker from L.A. Fitness in a strip center across the street, who buys coffee "just to grab all the customers who come in."

Janel Hall, who works at the Froots smoothie stand, says she'd probably get more business if Planet Fitness had a door leading into the mall.

Patrons come and go through an exterior door that doesn't provide mall access. Planet Fitness' owners say they needed the exterior entrance for convenience and that another door leading into the mall would make it difficult to keep track of people coming in.

"You used to drive by a brick wall," Ackerman said. "Now you drive by this beautiful, attractive, reconfigured entrance … I think it just makes the exterior more inviting."

Planet Fitness first opened a mall gym at Osceola Square last year.

At first, "we were a little nervous going into … a mall," said Eric Dore, managing partner of Planet Fitness' local franchise company.

But things have worked out well, he said.

Dore said Planet Fitness gets great perks from mall owners and management. "They're not afraid to spend money and give you great terms on a lease," he said.

Both malls paid to convert the space into gyms – around $600,000 apiece, Dore said. And the malls have helped with marketing more than the traditional strip centers where Planet Fitness centers typically open.

Malls bring other benefits as well.

"We need large parking lots, which is always a challenge for us and is often a deal breaker if we can't get comfortable with the parking," Dore said. "A lot of things we need are standard in a mall — the people, square footage, the marketing — the more we thought about it, the more it seemed like a natural fit."

The International Council of Shopping Centers did not have statistics, but spokesman Jesse Tron said fitness centers are on the rise in malls. They are just one of many types of nontraditional tenants that malls have brought in to fill vacancies, he said, bringing in more money and giving the centers a more vibrant feel.

Jim Pridemore, who runs a photography studio inside struggling Oviedo Marketplace, last year opened a fitness center in some vacant space there. The center, Snap Family Wellness, offers Zumba, yoga and circuit training.

Pridemore already had a fitness center outside the mall and said opening one at Oviedo Marketplace made sense.

Pridemore would not give specifics on what he paid for rent, but said it was a good deal.

"I think it's a trend people are going to see happen more and more," he said. "Malls are starting to think outside the box a little bit.''